Tapped for 10-32, made that way on purpose...The 5mm .8 stock carb bolts are about .006 larger and make for a good tight fit...You have to shorten the stock phillips head carb bolts to keep from bottoming out in the cylinder...
Use the stock bolts, just check the length first....The flatheads I use are 5mm .8 x 20 mm long, perfect fit in the cylinder and won't crack the insulator block..
You can take the disc out, won't hurt the shaft..Put some Loctite on the screw when you put it back in...Don't let the Loctite run down the shaft, it gets pretty tight...I KNOW